Tail lights, and signal lights have small bulbs with socket connections for coupling to a wire end power source. While there has been a constant drive to make the bulb coupling inexpensive, there has been a conflicting drive to make the coupling at least adequately if not completely water, salt, and vibration resistant. The most common taillight bulb is probably the bayonet type lamp, where the bulb base includes exterior contacts, and latches to couple with spring loaded contacts in a wire end socket. The bulb design is simple, and inexpensive, but total lamp function depends on the quality of the wire end socket provided by the automobile manufacturer. Unfortunately, the wire end sockets frequently have been equally simple. The wire end couplings may be bent, or twisted; or water, salt or dirt filled. The soldered, or clipped wire connections may also separate. The contacts corrode, and the spring contacts become intermittent. There are then lighting failures while the bulb is still good.
There is a trend to improve the taillight and marker light couplings, so the only possible lighting failure, is an actual failure of the lamp filament. The better couplings need strong matings with the wire end connector, and the lamp base. A need then exists for the lamp base side of the coupling to be improved to support such a strong mating. There is a further need for a strong coupling between the lamp leads, and the base coupling that can endure the extreme temperature, and environmental stresses that exist over the life of a vehicle.